This application is based on Japanese Patent Application No. 2002-100324 filed on Apr. 2, 2002, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an air conditioner with a heat pump refrigerant cycle. The air conditioner is suitably used for a vehicle.
2. Related Art
Generally, a heat pump refrigerant cycle is divided into a full heat pump system and a reversible heat pump system. In the full heat pump system, during a heating operation, air is firstly cooled in a cooling heat exchanger to a dew point so that moisture in the air is removed, and is heated by a heating heat exchanger disposed at a downstream air side of the cooling heat exchanger. On the other hand, in the reversible heat pump system, an interior heat exchanger and an exterior heat exchanger are provided, and a refrigerant flow in the interior heat exchanger and the exterior heat exchanger is reversed in the heating operation and a cooling operation. Specifically, by reversely changing the refrigerant flow, the interior heat exchanger cools air in the cooling operation, and heats air in the heating operation. However, in the reversible heat pump system, during the heating operation, air is not dehumidified in the interior heat exchanger, and a windshield of a vehicle is readily fogged.
Further, in a vehicle having a water-cooled engine, a heater core system using cooling water from the engine as a heating source is provided. In the heater core system, when temperature of cooling water of the engine is low, the interior heat exchanger of the heat pump system heats air to be blown into a passenger compartment. Thereafter, when the temperature of cooling water from the engine is sufficiently increased, the heat pump system is stopped, and air to be blown into the passenger compartment is heated by the heater core system using the cooling water as a heating source.
The heater core system may be simply combined with the full heat pump system. However, in this case, it is necessary to increase the sizes of the cooling heat exchanger and the heating heat exchanger of the full heat pump system, in order to obtain a sufficient air-conditioning capacity (cooling capacity or heating capacity). Further, in this system, refrigerant pipe structure becomes complex, and mounting performance of the air conditioner on the vehicle is deteriorated. On the other hand, the heater core system may be simply combined with the reversible heat pump system. However, in this case, when the temperature of the engine-cooling water is low in the heating operation, because the interior heat exchanger is used for heating air, air is not dehumidified.
In view of the above-described problems, it is an object of the present invention to provide an air conditioner with a new system structure.
It is another object of the present invention to provide an air conditioner that has a simple system structure while improving dehumidifying capacity of air.
According to the present invention, in an air conditioner for a compartment, a refrigerant cycle system includes a compressor for compressing and discharging refrigerant, an exterior heat exchanger for performing heat exchange with outside air outside the compartment, an interior heat exchanger for cooling and heating air to be blown into the compartment, a cooling heat exchanger in which the refrigerant flows for cooling air to be blown into the compartment, and a decompression device for decompressing the refrigerant flowing to the cooling heat exchanger. Further, the interior heat exchanger is disposed such that the refrigerant discharged from the compressor flows to the interior heat exchanger after passing through the exterior heat exchanger in a cooling operation for cooling the compartment, and the refrigerant discharged from the compressor flows to the exterior heat exchanger after passing through the interior heat exchanger in a heating operation for heating the compartment. Accordingly, in the heating operation, the interior heat exchanger heats air flowing through the air passage by radiating heat from the refrigerant, and the cooling heat exchanger cools air flowing through the air passage by evaporating the refrigerant. On the other hand, in the cooling operation, at least the interior heat exchanger cools air flowing through the air passage by evaporating the refrigerant. Accordingly, the air conditioner has an improved system structure of the refrigerant cycle.
In addition, in the air conditioner, the decompression device is opened even in the cooling operation. Therefore, in the cooling operation, both the cooling heat exchanger and the interior heat exchanger can be used for cooling air to be blown into the compartment. Therefore, it can restrict condensed water from being largely generated on the interior heat exchanger in the cooling operation, and it can effectively prevent a windshield from being fogged at a switching time from the cooling operation to the heating operation, when the air conditioner is used for a vehicle. Accordingly, dehumidifying capacity of air can be improved while the refrigerant cycle has a simple structure.
Here, the cooling heat exchanger can be disposed upstream from the interior heat exchanger in an air flowing direction. Alternatively, the cooling heat exchanger and the interior heat exchanger can be disposed in the air conditioning case, in parallel in the air flowing direction.
Preferably, the cooling heat exchanger and the interior heat exchanger are disposed such that at least a part of air after passing through the cooling heat exchanger passes through the interior heat exchanger. Therefore, in the air conditioner, air can be effectively dehumidified while it can restrict the temperature of air blown into the compartment from being greatly decreased.
Preferably, the cooling heat exchanger is coupled to the interior heat exchanger such that at least a part of refrigerant flowing out from the interior heat exchanger is introduced to the cooling heat exchanger. Alternatively, the cooling heat exchanger is coupled to the interior heat exchanger such that refrigerant flowing to the cooling heat exchanger is branched from the interior heat exchanger. Accordingly, refrigerant can be readily introduced into the cooling heat exchanger with a simple structure.
The refrigerant cycle of the air conditioner further includes an inner heat exchanger for performing a heat exchange between a high-pressure side refrigerant before being decompressed, and a low-pressure side refrigerant after being decompressed. Further, the inner heat exchanger has therein a first refrigerant passage through which the high-pressure side refrigerant flows, and a second refrigerant passage through which the low-pressure side refrigerant flows. In this case, the first refrigerant passage has a passage diameter that is substantially equal to a passage diameter of the second refrigerant passage. Alternatively, the first refrigerant passage has an equivalent passage diameter that is substantially equal to that of the second refrigerant passage. Therefore, even when refrigerant reversely flows through the inner heat exchanger, it can prevent heat-exchanging capacity of the inner heat exchanger from being greatly decreased.